1. Field of the Invention
Systems and methods consistent with the present invention relate to a Universal Plug-and-Play (UPnP)-based network, and, more particularly, to a UPnP-based network system and a control method thereof that can support a dynamic change of a service provided in a mobile network environment.
2. Description of the Prior Art
UPnP is a representative protocol for home networks.
UPnP technology is an architecture for a peer-to-peer connectivity of all types of intelligent products, wireless devices, and personal computers (PCs). UPnP has been designed to be easily used in homes, small offices, public places, ad-hoc networks connected to the Internet, or in an unmanaged networks, to have flexibility, and to provide connectivity based on the standards. UPnP technology provides a distributed open network architecture that enables Transmission Control Protocol (TCP)/Internet Protocol (IP) and Web technology to perform seamless proximity networking. That is, UPnP technology provides connectivity and interoperability among services in a distributed computing environment.
FIG. 1 is a view illustrating the construction of a general home network system.
In a home network, a UPnP-based network system may be logically divided into two parts. One is a controlled device (hereinafter referred to as a “CD”) that provides the inherent service of a device and is controlled by a user, and the other is a control point (hereinafter referred to as a “CP”) that provides functions capable of controlling home devices. That is, the CP corresponds to a client, and the CD corresponds to a service or a device that provides the service.
As illustrated in FIG. 1, in the home network system, a plurality of UPnP-based network systems 110, 120, 130, 140, and 200 may be connected to one another. For example, a UPnP-based CP may be a computer 110, a personal digital assistant (PDA) or portable phone 120, a printer 130, or a notebook computer 140, and a UPnP-based CD may be a server 200 for providing a service.
The UPnP device architecture defines a communication protocol between the CP and the CD that is controlled by the CP. That is, all devices existing on the home network transmit UPnP protocols for mutual communications.
FIGS. 2A to 2D are views illustrating a communication process between general UPnP-based network systems.
In the UPnP-based network, the communications can be divided into the steps of discovery, description, control, eventing, and presentation.
FIG. 2A shows the UPnP-based discovery step, which can be divided into two processes.
One is a process in which a CD sends device information or service information that can be provided by the CD itself in a multicast method, i.e., a process of transmitting an advertisement message (S10), and the other is a process in which a CP searches for a concerned CD on a home network, i.e., a process of transmitting a search message to the CD (S20). Accordingly, the CP receives a response message in a unicast form from the CD (S30). In contrast, in a step where the CD leaves the home network, the CD sends a bye message in a multicast form to the CP.
FIG. 2B shows the UPnP description step, which is a step in which the CP acquires a device of the CD to be controlled by the CP and description information of a service.
That is, the UPnP requests and receives a device description file (S40 and S45) and a service description file (S50 and S55) of the corresponding CD based on description URL information of the corresponding CD acquired through the discovery step.
FIG. 2C shows the UPnP control step, which is a step of transmitting/receiving a control command between the CP and the CD. In the control step, a response message is provided in response to a request message (S60 and S65).
FIG. 2D shows the UPnP eventing step, which is a step in which the CP receives an event message according to the state change of a service from the CD.
In order for the CP to receive an event message according to the state change of a service from the CD, it should be first registered in the CD through the subscription step (S70 and S75). Then, if the state change of the service provided from the CD or a specified eventing situation is generated, the CD transmits the corresponding event message to the registered CP (S80). In contrast, the CP can set a timeout at the subscription step, and can make a renewal request within the timeout period. In addition, if the CP no longer wants to receive the event message from the CD, it may request cancellation.
However, the related art UPnP-based network system and the control method thereof have the following problems.
Even if the service is dynamically changed such as addition of a new service to the CD, the CP determines only whether a new device is added by confirming a unique device name (UDN) in an advertisement message, and thus it becomes impossible to recognize the addition of a service such as the addition of a new service or deletion of the service. This is because, in the UPnP-based CD, the addition or deletion of a service corresponds to the characteristic of a static home network environment. However, the addition or deletion of a service is required in the mobile network environment, and thus the existing PnP technology has limitations in this regard.